1. Field of the Invention
This invention generally relates to time-domain reflectometry. In particular, this invention relates to systems and methods for calibrating a time-domain reflectometer to precisely determine the reflectometer's response when connected to an electrical network.
2. Description of Related Art
Time-domain reflectometry (TDR) systems use electrical measurements to estimate the physical structure and electrical nature of a conducting medium, which will be referred to herein as the Device Under Test (DUT). An example of a DUT is a twisted pair subscriber line, which comprises one or more interconnected electrical transmission lines generally having unknown terminations. Features of the DUT that can be estimated include the length of the line, the existence of bridged taps, the bridged tap locations, the bridged tap lengths, changes in gauge, terminations, and the like. Exemplary DUTs, such as subscriber lines, are constructed of twisted pairs, which distort the amplitude and phase of electrical waveforms that propagate through the line. Since, the amplitude of the waveforms decrease exponentially with travel distance, the waveforms received from long subscriber lines are extremely weak and require a precise TDR system to capture minute variations that contain information about the characteristics of the subscriber line.